Unless you're keeping it 75F or warmer in there you shouldn't be using a delta-T of 60F, given that your 99% outside design temp is +15F (+ 60F = 75F).

The Burnham tool is pretty crappy, and you've haven't been anywhere near aggressive enough on the R/U & air tightness assumptions. The instructions for Manual-J are to use the most aggressive assumptions possible that are still at least somewhat realisitic, and that goes for other tools too.

If you just scale their 70F delta to a 55F delta (70F-15F = 55F) you get 55/60 x 59,296 = 54,355 BTU/hr which is probably still more than 2x (100%) higher than your actual heat load at +15F outside/70F inside.

The code mininum interior design temp is 68F, so it's really a 53F delta unless you're intentionally padding it.

In addition to sailawayrb's picks, a better easy to use quickie online heat load tool is loadcalc.net (http://loadcalc.net/ ). It will also overshoot reality (as determined by more sophisticated aggressive Manual-Js and fuel use analysis) almost every time by at least 20%, sometimes over 40% but not by 75-100%. To get even that close you have to select for tight construction rather than "average", and make the most aggressive assumptions possible about R-values shading factors, air tightness, etc. They use +15F for the design temp for Central Islip, which is consistent with most design temps for L.I. (What's your actual ZIP code?) With the loadcalc tool using aggressive numbers you should NOT oversize the boiler from whatever it comes up with- it's usually already well padded, but won't be 2x reality.

The 1.4x oversizing factor is really a maximum, from an aggressively calculated load, and where appropriate only applies to high mass non-modulating boilers such as cast iron. It's not really necessary, and anything between 1.0x and 1.4x oversizing will be fine, even when it's 0F out.

Seriously, a cheaper stainless fire tube mod-con like the Weil McLain ECO-70 or HTP UFT-080W and an indirect will cover your loads with margin, and can usually be installed for less money than an ES2-3/ES2-4 since they can be side vented, and won't need a new flue liner. The UFT-080W boiler is even cheaper than an ES2-3, the ECO-70 runs about the same as the ES2-4 at internet pricing.

https://www.weil-mclain.com/sites/default/files/field-file/eco-brochure_0.pdf

http://www.htproducts.com/literature/UFTWallFloor-Brochure.pdf

The ~13K minimjm-fire output of the ECO 70 is probably still about 1/2 your design-day heat load so it'll cycle a bit during the shoulder seasons, but you have enough radiation to run it in condensing mode and hit it's AFUE numbers. The UFT-080W can modulate down to ~7.5K out in condensing mode which is probably about 1/3 of your design heat load, and set up properly should modulate more, cycle less. Either can still deliver the ~65K max your radiation can emit, in the event that you own actually DO own the crappiest 1450' house on Long Island and actually NEED that much heat.

For the napkin-math on how to NOT oversize a modulating condensing boiler and short-cycle it into low efficiency and an early grave, see:

http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/sizing-modulating-condensing-boiler

When running the heat load tools, use the "after" picture of any intended upgrades. Most older homes with basements don't have foundation insulation and leak a fair amount of air at the foundation sill and band joist. Even if you don't fully finish the basement, insulating it to the IRC 2015 code min R10 continuous insulation with rigid foam is usually "worth it" as a DIY project, using 2" reclaimed roofing polyiso strapped to the foundation with 1x4s through=screwed to the foundation with 4" masonry screws, mounting wallboard (a code require ignition barrier for the foam) on the furring. While a 2x4/R13 studwall would also meet code performance that approach creates a high mold risk. At least an inch of rigid foam (any type) between the studwall and foundation would be needed to control moisture, and it ends up eating into the interior space a bit more. A shot of 1.5-2" closed cell polyurethane on the bandjoist & foundation sill and the top of the foundation out to the top of your wall foam seals & insulates it (at ~$2-2.50 per square foot for HFC blown goods- which are environmentally bad, up to ~$3 square foot for much more benign HFO blown foam.)

Rigid foam reclaimers often advertise here:

https://longisland.craigslist.org/search/sss?query=rigid+insulation

Posted By sailawayrb on 18 Apr 2018 01:57 PM
53F seems like a more reasonable delta T. ASHRAE recommends getting a heat source 40% larger than the actual heat loss at the local 99% dry bulb temp. The thinking here is largely to accommodate nighttime thermostat setback...getting a larger heat source to handle heating up the typical house furnishings in addition to the air in the morning in a reasonable amount of time. If you have a high interior thermal mass house (e.g., concrete slab floors and masonry walls, etc.), you should NOT use nighttime thermostat setback. As a house becomes more energy efficient (i.e., is well-insulated and well-sealed), the benefit of using nighttime thermostat setback tends to zero. If you don’t use nighttime thermostat setback, I would NOT recommend applying this 1.4 factor to the heat loss estimate for sizing the heat source.

Thank you much for the wisdom! and new heat loss /energy usage links. Will have to really sit down 1 day and do a hard number calc.
I think I'm on board now. Probably will use a delta T of 55 in the future. I think my current rental is set at 73.4F (we use Celsius on the Thermostat). Different house I know but we like it hot.
Also i do use thermostat setback now in my current house but on the new boiler I asked for outdoor reset. If I have that I should just let the electronics do their thing right and not setback at all?

Posted By Dana1 on 18 Apr 2018 03:39 PM
Unless you're keeping it 75F or warmer in there you shouldn't be using a delta-T of 60F, given that your 99% outside design temp is +15F (+ 60F = 75F).

The Burnham tool is pretty crappy, and you've haven't been anywhere near aggressive enough on the R/U & air tightness assumptions. The instructions for Manual-J are to use the most aggressive assumptions possible that are still at least somewhat realisitic, and that goes for other tools too.

If you just scale their 70F delta to a 55F delta (70F-15F = 55F) you get 55/60 x 59,296 = 54,355 BTU/hr which is probably still more than 2x (100%) higher than your actual heat load at +15F outside/70F inside.

The code mininum interior design temp is 68F, so it's really a 53F delta unless you're intentionally padding it.

In addition to sailawayrb's picks, a better easy to use quickie online heat load tool is loadcalc.net (http://loadcalc.net/ ). It will also overshoot reality (as determined by more sophisticated aggressive Manual-Js and fuel use analysis) almost every time by at least 20%, sometimes over 40% but not by 75-100%. To get even that close you have to select for tight construction rather than "average", and make the most aggressive assumptions possible about R-values shading factors, air tightness, etc. They use +15F for the design temp for Central Islip, which is consistent with most design temps for L.I. (What's your actual ZIP code?) With the loadcalc tool using aggressive numbers you should NOT oversize the boiler from whatever it comes up with- it's usually already well padded, but won't be 2x reality.

The 1.4x oversizing factor is really a maximum, from an aggressively calculated load, and where appropriate only applies to high mass non-modulating boilers such as cast iron. It's not really necessary, and anything between 1.0x and 1.4x oversizing will be fine, even when it's 0F out.

Seriously, a cheaper stainless fire tube mod-con like the Weil McLain ECO-70 or HTP UFT-080W and an indirect will cover your loads with margin, and can usually be installed for less money than an ES2-3/ES2-4 since they can be side vented, and won't need a new flue liner. The UFT-080W boiler is even cheaper than an ES2-3, the ECO-70 runs about the same as the ES2-4 at internet pricing.

https://www.weil-mclain.com/sites/default/files/field-file/eco-brochure_0.pdf

http://www.htproducts.com/literature/UFTWallFloor-Brochure.pdf

The ~13K minimjm-fire output of the ECO 70 is probably still about 1/2 your design-day heat load so it'll cycle a bit during the shoulder seasons, but you have enough radiation to run it in condensing mode and hit it's AFUE numbers. The UFT-080W can modulate down to ~7.5K out in condensing mode which is probably about 1/3 of your design heat load, and set up properly should modulate more, cycle less. Either can still deliver the ~65K max your radiation can emit, in the event that you own actually DO own the crappiest 1450' house on Long Island and actually NEED that much heat.

For the napkin-math on how to NOT oversize a modulating condensing boiler and short-cycle it into low efficiency and an early grave, see:

http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/sizing-modulating-condensing-boiler

When running the heat load tools, use the "after" picture of any intended upgrades. Most older homes with basements don't have foundation insulation and leak a fair amount of air at the foundation sill and band joist. Even if you don't fully finish the basement, insulating it to the IRC 2015 code min R10 continuous insulation with rigid foam is usually "worth it" as a DIY project, using 2" reclaimed roofing polyiso strapped to the foundation with 1x4s through=screwed to the foundation with 4" masonry screws, mounting wallboard (a code require ignition barrier for the foam) on the furring. While a 2x4/R13 studwall would also meet code performance that approach creates a high mold risk. At least an inch of rigid foam (any type) between the studwall and foundation would be needed to control moisture, and it ends up eating into the interior space a bit more. A shot of 1.5-2" closed cell polyurethane on the bandjoist & foundation sill and the top of the foundation out to the top of your wall foam seals & insulates it (at ~$2-2.50 per square foot for HFC blown goods- which are environmentally bad, up to ~$3 square foot for much more benign HFO blown foam.)

Rigid foam reclaimers often advertise here:

https://longisland.craigslist.org/search/sss?query=rigid+insulation

Thank you Dana1.
I will use a delta T of 55 in the future. I think my current rental is set at 73.4F (we use Celsius on the Thermostat). Different house I know but we like it hot.
Herein lies the problem. I put a deposit in already for the contractor so I'm neither here nor there. I'm going to eat it somewhere.... He is old school and hasn't had worthwhile success with mod condensing boilers etc. According to him, the costs in service and lack of longevity outweigh the efficiency savings. He still adamantly suggested that the ES2-4 was the correct size and that the Board of Health wouldn't accept less but after a long talk and accepting liability if it doesn't heat well enough, I at least got him to get the boiler down to ES2-3. Plus it will get the outdoor reset. So it's still oversized but less so.... Even then he was sure that was insufficient! My fault for not finding this site prior.
Ill have to start saving for my additions.
One of my first to dos was to insulate the basement walls. However three things - there is one section where pipes run too close to the wall for me to do anything (maybe like 15% of the linear wall area), i have a water problem at one window, and finally termites. I was just going to spray foam the rim joist but then the termite people were like that's the worst thing to do... I don't know any more... The window I have to either redo the framing or may just seal it up with brick (not sure whether permits needed). The wall I can do except the part of wall with pipes - not sure if i just don't do that part or move all pipes or what...

With a modulating condensing boiler with the outdoor reset dialed-in it's normal to "set and forget" overnight setbacks. Some mod-cons allow programming two curves, one for the setback, one for the normal indoor temp, and a programmed "boost" adder to raise the water temp for the recover ramp. All of that it more than you really need or want (unless you're super fussy.)

There really isn't much efficiency to be gained using outdoor reset on an oversized non-modulating cast iron boiler. The ES2 series is internally protected from 110F return water from radiation with plumbing inside the sheet metal, but sets the boiler's low limit to 140F to prevent damaging condensation inside the boiler. But if your radiation can deliver 65K at an entering water temp (EWT) or average water temp (AWT) of 180F (which is typically where high temp heating systems are designed) it'll still deliver ~33K+ at an EWT of 140F. Your actual design heat load is probably less than 25K, and almost certainly less than 33K, so you'll never actually NEED water hotter than the 140F minimum of the boiler. You may not even need water hotter than ~120F to deliver the design-day heat, but we can ball-park that better when we have better load numbers.

Outdoor reset adjusts the water temperature up to compensate for lower outdoor temperatures so that the heat emitted by the radiation always matches the heat loss of the house in real-time, so that room temperatures remain stable. But when the design day water temperature requirements are lower than the minimum safe operating temperature of the boiler, outdoor reset on the boiler isn't going to do ANYTHING for comfort or efficiency, since it never needs to run above it's minimum temp, and isn't allowed to operate below that temperature.

Using a mixing valve with outdoor reset (eg Taco I-series) to allow water cooler than the boiler's minimum to circulate in the radiation can work, and provide higher comfort with lower distribution losses to the basement, but it's a pretty marginal efficiency boost compared to a modulating condensing boiler that can run almost arbitrarily low output temperatures, and reap a large efficiency boost out of it while doing so.

I wish more boiler installers would actually do enough math to at least try to size the boiler to the actual heat loss of the house, but they don't. This guy at least gave a shot at not grossly oversizing the boiler to the radiation (which also happens- a lot), but the radiation is oversized for heating the house at cast-iron boiler operating temperatures. The oversized radiation is often an artifact of the evolution of the house, which may have started out with essentially no insulation, single-pane windows without storms, and a design mentality that assumed bigger is better installing a system 2x oversized for the original house. When the house gets insulated and the windows upgraded the radiation is then 3x+ oversized for heating the house with high temp water. That's great if it allows you to then run with a low-temp condensing boiler, not so much if going with non-modulating cast-iron. A right-sized cast iron boiler for the heat load would then have to be protected from condensing return water temperatures, the very thing that you WANT with a condensing boiler. That's just one reason why some contractors prefer to size the boiler at the high-temp output of the radiation- they don't have to design in that protection or deal with boiler failures due to condensation on the boiler plates if they don't.

Posted By Dana1 on 18 Apr 2018 07:08 PM
I wish more boiler installers would actually do enough math to at least try to size the boiler to the actual heat loss of the house, but they don't. This guy at least gave a shot at not grossly oversizing the boiler to the radiation (which also happens- a lot), but the radiation is oversized for heating the house at cast-iron boiler operating temperatures. The oversized radiation is often an artifact of the evolution of the house, which may have started out with essentially no insulation, single-pane windows without storms, and a design mentality that assumed bigger is better installing a system 2x oversized for the original house. When the house gets insulated and the windows upgraded the radiation is then 3x+ oversized for heating the house with high temp water. That's great if it allows you to then run with a low-temp condensing boiler, not so much if going with non-modulating cast-iron. A right-sized cast iron boiler for the heat load would then have to be protected from condensing return water temperatures, the very thing that you WANT with a condensing boiler. That's just one reason why some contractors prefer to size the boiler at the high-temp output of the radiation- they don't have to design in that protection or deal with boiler failures due to condensation on the boiler plates if they don't.

How do these installers not get crazy calls about short cycling on these seriously oversized boilers? Or is it like a silent killer reducing lifespan of the unit and wasting fuel but not enough for anyone to notice/care?

Most people don't even notice whether the boiler is cycling on/off when the circulation pumps are running, or they think it's normal for the system to behave that way. They only consider it a problem if the radiation (or house) gets cold. They don't have a parallel universe to compare the fuel use numbers with something more right-sized for the same house & radiation.

Boilers will only short cycle if oversized for the radiation, so if the radiation is 4x oversized for the house it's not a problem for the longevity of the boiler as long a the boiler isn't too oversized for the radiation. But the lower seasonal average duty cycle and resulting higher standby losses take a toll on system efficiency. If the burner is only running a 25% duty cycle at design condition (4x oversizing) the seasonal average duty cycle could even be in single digits, spending 90%+ of the time in standby, and deliver an as-used AFUE well below the test numbers. As long as the boiler's output isn't too far ahead of the radiation's output it can go a long long time, even at ridiculous oversizing levels.

Most boilers will at least survive the warranty period even when short cycling, despite the excessive wear & tear. But it'll knock another 10% or more off the as-used efficiency if the burns are under 5 minutes with 10 burns or more per hour (true short-cycling.) With most cast iron at 10 minute burns the average combustion efficiency is very close to it's steady-state efficiency, but the hit isn't more than a percent or two if it's at least delivering 5 minute burns. South of three minute burns with a dozen ignition cycles per hour it's headed over an efficiency cliff. Short cycling is a different problem from merely having a low seasonal average duty cycle.

Posted By Dana1 on 18 Apr 2018 07:08 PM
There really isn't much efficiency to be gained using outdoor reset on an oversized non-modulating cast iron boiler. The ES2 series is internally protected from 110F return water from radiation with plumbing inside the sheet metal, but sets the boiler's low limit to 140F to prevent damaging condensation inside the boiler. But if your radiation can deliver 65K at an entering water temp (EWT) or average water temp (AWT) of 180F (which is typically where high temp heating systems are designed) it'll still deliver ~33K+ at an EWT of 140F. Your actual design heat load is probably less than 25K, and almost certainly less than 33K, so you'll never actually NEED water hotter than the 140F minimum of the boiler. You may not even need water hotter than ~120F to deliver the design-day heat, but we can ball-park that better when we have better load numbers.

Outdoor reset adjusts the water temperature up to compensate for lower outdoor temperatures so that the heat emitted by the radiation always matches the heat loss of the house in real-time, so that room temperatures remain stable. But when the design day water temperature requirements are lower than the minimum safe operating temperature of the boiler, outdoor reset on the boiler isn't going to do ANYTHING for comfort or efficiency, since it never needs to run above it's minimum temp, and isn't allowed to operate below that temperature.

I was reading up on the ES2 settings and Outdoor Reset. Hoping you could make some suggestions on fine tuning IF i end up not getting the Outdoor reset and thus have to adjust myself. It appears that you cannot mess with the low limit. That is controlled by the boiler itself though in the manual for the outdoor reset it looks like it can go down to 130F (that as I understand is to stop chimney gas/boiler condensation). That would also make sense since you can set the high limit and it's low value is listed at 140F. According to the literature it says it runs more efficient if it runs at lower temp...

Keeping in mind that I have baseboard/convector radiators on a 1 pipe system and an oversized radiator =P
Let's say I set the High limit in the extreme down to 145F or even 140F (assuming that the return water will come back above 110F, how do i figure that out?)
Then set the High Limit Differential to the minimum of 10F (then it should kick in before the internal low limit)
Start temp default to 140F (that should be ok for my baseboard/convectors. then "useful heat" difference btw Boiler temp and Start temp is 5F - is that ok?)

Circulator Overrun time maybe helpful? a couple of mins maybe? Can do 0-10 mins
Circulator Pre Purge time won't really be applicable since the boiler won't really be much warmer than the 140 set point.
Hot water stuff not applicable (maybe swap to indirect later) Instead of Hot water can be turned into another heat zone which I toyed with making the upstairs separate from the downstairs but that would make the system more efficient which would cut my boiler run times more right?

The other problem with operating under outdoor reset with non-modulating boilers is the increased cycling. At your intended 135-145F average output temp instead of emitting the 65.000 BTU/hr it will be emitting 30-33,000 BTU/hr, enough to heat your house even at 0F or colder, but it makes the ES2-4 more than 3x oversized for the radiation at that water temp, and the ES2-3 would be about 2x oversized. You'll get fewer cycles and better efficiency by running it at a higher temperture and letting it pre-purge down to 140F, despite the slightly higher raw combustion efficiency at 140F than at 180F.


A typical condensing curve looks like this: http://www.healthyheating.com/Boilers/Images/Boiler2.gif

With return water entering the boiler's heat exchangers at say 170F you'll get about an 85% combustion efficiency. At 130F entering water temp (which is probably where the internal compensation in the ES2 is set for when return water temps are cooler), it'll run about 87% raw combustion efficiency, a ~2% improvement. If the burn cycles are 5 minutes when running at lower temp any potential savings from the higher combustion efficiency are more than erased by the cycling losses. If the burn times are 10 minutes or longer they'll be real. The total thermal mass in the system (mostly the water volume), the temperature swing from beginning of burn to the end of burn, and the amount of "excess" heat going into the radiation that isn't being emitted determine the burn times. The lower the high-limit (as in outdoor reset control) the greater the excess heat (since the radiation emits less), and the lower the temperature swing, all trending toward shorter burn times, higher cycling rates.

If an ES2 boiler is really what you're installing you'll have to play around with the temperature settings and MEASURE the return water temps to keep them above 110F, and MEASURE the burn times and total duty cycle during continuous calls for heat. The ES2=4 is already oversized for the radiation even at high temp, and will cycle a lot more with the high limit set to 145F. With the ES2-3 there would be at least some temperature at which it would burn continuously during calls for heat.

Circulator over-run is a post-purging of heat from the boiler putting in into the fully conditioned space rooms. That is beneficial for efficiency since it parks the boiler at a lower temp between calls for heat, lowering the standby losses, but may also cause overshoots on the room temperatures under some conditions. It's worth playing with, especially if you have to run the boiler at higher temp to keep the burn times reasonable.

Breaking the system into multiple zones makes the boiler even MORE oversized for the individual zone radiation. With a modulating boiler as long as the zone radiation emits something comparable to the minimum firing rate that can be fine. With an oversized cast iron boiler it adds a lot of cycling. If the boiler is already 50% oversized for the whole house radiation even at high temp and you split the radiation into equal halves, it'll be 2x oversized for any single zone (even at high temp), and ludicrously oversized if you're running the boiler at 145F high-limit, pretty much guaranteeing short-cycling. When you get to the point where you have to add buffer tanks for more thermal mass to keep the minimum burn times reasonable on zone calls it's time to have your head examined to figure out what you're really trying to do.

If you break it up into zones, installing a "reverse indirect" water heater as a central buffer tank with an internal coil containing the potable water might make sense. Even a 25-30 gallon buffer tank has enough thermal mass to add a precious seconds or minutes to the minimum burn time to allow even smaller zoning. eg: http://www.ergomax.com/new-tanks.htm http://www.thermo2000.com/pdf/en-US/specs/specifications_turbomax.pdf

They're pretty expensive compared to a regular indirect, but cheaper than a standard indirect + buffer tank. With a 100K boiler such as the ES2-4 and minimum storage temp of 140F on the buffer tank you won't run out of water even with a ~25-35 gallon reverse indirect unless you have a huge soaking tub or something. Even if the radiation is pulling 35KBTU/hr out of the tank a 100K boiler is still putting enough back in enough to simultaneously cover a 2.5 gpm shower.

Posted By Dana1 on 19 Apr 2018 03:37 PM
The other problem with operating under outdoor reset with non-modulating boilers is the increased cycling. At your intended 135-145F average output temp instead of emitting the 65.000 BTU/hr it will be emitting 30-33,000 BTU/hr, enough to heat your house even at 0F or colder, but it makes the ES2-4 more than 3x oversized for the radiation at that water temp, and the ES2-3 would be about 2x oversized. You'll get fewer cycles and better efficiency by running it at a higher temperture and letting it pre-purge down to 140F, despite the slightly higher raw combustion efficiency at 140F than at 180F.


A typical condensing curve looks like this: http://www.healthyheating.com/Boilers/Images/Boiler2.gif

With return water entering the boiler's heat exchangers at say 170F you'll get about an 85% combustion efficiency. At 130F entering water temp (which is probably where the internal compensation in the ES2 is set for when return water temps are cooler), it'll run about 87% raw combustion efficiency, a ~2% improvement. If the burn cycles are 5 minutes when running at lower temp any potential savings from the higher combustion efficiency are more than erased by the cycling losses. If the burn times are 10 minutes or longer they'll be real. The total thermal mass in the system (mostly the water volume), the temperature swing from beginning of burn to the end of burn, and the amount of "excess" heat going into the radiation that isn't being emitted determine the burn times. The lower the high-limit (as in outdoor reset control) the greater the excess heat (since the radiation emits less), and the lower the temperature swing, all trending toward shorter burn times, higher cycling rates.

If an ES2 boiler is really what you're installing you'll have to play around with the temperature settings and MEASURE the return water temps to keep them above 110F, and MEASURE the burn times and total duty cycle during continuous calls for heat. The ES2=4 is already oversized for the radiation even at high temp, and will cycle a lot more with the high limit set to 145F. With the ES2-3 there would be at least some temperature at which it would burn continuously during calls for heat.

Circulator over-run is a post-purging of heat from the boiler putting in into the fully conditioned space rooms. That is beneficial for efficiency since it parks the boiler at a lower temp between calls for heat, lowering the standby losses, but may also cause overshoots on the room temperatures under some conditions. It's worth playing with, especially if you have to run the boiler at higher temp to keep the burn times reasonable.

yeah it's going to be the ES2-3.
In the above scenario I was trying to run it at a lower temp thinking a) it be enough to heat the house (check) and b) it would cycle less/increase burn times (you are saying it will probably cycle more)
With lower return water the boiler is more efficient but it makes a net difference only if it cycles less/ burn times end up being greater than 10 mins.

If I understand you right, instead I should set the high limit at 180F, set the max differential to 30F (too much?) so that the boiler can get down to 140F or so before re-firing, pre-purge to max time of 20 mins because if it drops below 140F it will override and kick on boiler anyway, and I let the circulator overrun a tiny bit because I want the boiler to lower the standby losses though it's not the end of the world because I'm losing this heat into the basement right?.
Here's where I start to get confused and this is probably all boiler 101.
What happens if the boiler hits the low limit and there is no call for heat? Does it simmer at or around the low limit, does it burn to the high limit? Something in between?
In my case, if there is a call for heat, Since the boiler is oversized it would satisfy quick and the burn would stop just as quick? Lets say i set 72F on the Tstat and the heat call comes on a few degrees lower. What is the likely temperature swing from beginning of burn to the end of burn in my scenario? Just a little? Or does it burn until the high limit? And we could obviously tweak the water volume by adding water in the form of a buffer tank...

You can use this software to determine what the actual boiler cycle time will be given your boiler settings and system fluid volumes or you can design/size a buffer tank given your boiler settings, system fluid volumes and your desired cycle time:

Borst Buffer Tank Design Software

However, I would recommend avoiding a buffer tank completely whenever possible.

You probably won't need 20 minutes of pre-purge to hit 140F, especially if you post-purge. The real savings will be on post-purge anyway, bringing the standby temp (and thus the standby losses) way down. Yes, set the differential to the maximum, then see how the system behaves. If the max diff is 30F, set the high-limit to (140F +30F=) 170F.

With the ES2-3 you have enough radiation that it won't be cycling at all on continuous calls for heat at high temp, and probably won't be able to fully reach 180F, but might be able to hit 170F. But post-purging it from 170F (or wherever it actually stabilizes during a long call for heat), down to 140-145F will make a large difference in the standby loss.

I believe Burnham's gas boilers are all cold-startable, and won't fire to maintain 140F unless there is an active call for heat. During an active call for heat it will fire when it hits the low-limit temp, and pre-purging will still buy you something real but utilizing all of the residual heat in the boiler left over from the last post-purge.

I'm guessing that the contractor's radiation output estimate of 67K was based an an EWT of 180F, AWT of 170F. The same radiation emitting the ES2-3s full DOE output of 59K the AWT is going to balance a temperature about 10F cooler than that, or about 160F AWT, maybe a bit less if there is much distribution loss before the first convector (probably not- especially if the plumbing is insulated, which it SHOULD be.) Depending on the actual flow rates that could be ~170F out of the boiler, 150F return, or maybe 165F out, 155F return, or maybe 165F out, 150F return, any of which is fine. With a post purge the boiler's temp should drop under 150F fairly rapidly (probably less than 5 minutes), but you can experiment with that a bit. I'm not sure if the boiler's controls would allow it to post-purge to under 140F, but you can find that out experimentally too (if it's not in the documentation.) If running the post-purge another 3-5 minutes drops it to 130F, so much the better. At some point the amount of pre & post purge pumping power starts to add up, so there's not much point to super-long purges, especially since the boiler won't ever be over the ~170F mark.

Posted By Dana1 on 19 Apr 2018 07:10 PM
You probably won't need 20 minutes of pre-purge to hit 140F, especially if you post-purge. The real savings will be on post-purge anyway, bringing the standby temp (and thus the standby losses) way down. Yes, set the differential to the maximum, then see how the system behaves. If the max diff is 30F, set the high-limit to (140F +30F=) 170F.

With the ES2-3 you have enough radiation that it won't be cycling at all on continuous calls for heat at high temp, and probably won't be able to fully reach 180F, but might be able to hit 170F. But post-purging it from 170F (or wherever it actually stabilizes during a long call for heat), down to 140-145F will make a large difference in the standby loss.

I believe Burnham's gas boilers are all cold-startable, and won't fire to maintain 140F unless there is an active call for heat. During an active call for heat it will fire when it hits the low-limit temp, and pre-purging will still buy you something real but utilizing all of the residual heat in the boiler left over from the last post-purge.

I'm guessing that the contractor's radiation output estimate of 67K was based an an EWT of 180F, AWT of 170F. The same radiation emitting the ES2-3s full DOE output of 59K the AWT is going to balance a temperature about 10F cooler than that, or about 160F AWT, maybe a bit less if there is much distribution loss before the first convector (probably not- especially if the plumbing is insulated, which it SHOULD be.) Depending on the actual flow rates that could be ~170F out of the boiler, 150F return, or maybe 165F out, 155F return, or maybe 165F out, 150F return, any of which is fine. With a post purge the boiler's temp should drop under 150F fairly rapidly (probably less than 5 minutes), but you can experiment with that a bit. I'm not sure if the boiler's controls would allow it to post-purge to under 140F, but you can find that out experimentally too (if it's not in the documentation.) If running the post-purge another 3-5 minutes drops it to 130F, so much the better. At some point the amount of pre & post purge pumping power starts to add up, so there's not much point to super-long purges, especially since the boiler won't ever be over the ~170F mark.

Fascinating stuff! Dana1 let me run this by you.

If the goal is to get the boiler to 170F each time, I can actually artificially do that because it has a start temp setting that adjusts for different heating radiation. The range is 140F to 180F. If I dial it to 170F, the water won't begin circulating before then is how I understand it. So each call for heat would require it to heat it until that temp. The actual heat demand should be satisfied quite quickly thereafter since that would be more than sufficient to load up my system. Then I can post purge it for 5-8 minutes and get the boiler down to 145-150F. I would probably have to lower thermostat because the system would overshoot the temp with the post purge. The only other thing is it probably kills off the pre-purge because I assume with the start temp at 170F it won't have enough to meet the criteria for a pre-purge... It would be in effect forcing it to heat from baseline standing temp to 170F each time ensuring I have decent burn time, post purge to reduce standby losses getting it down to ~150F using the most of each burn. Rinse and repeat... Is that logic sound?

On the insulation part - You mean just in the basement right? Don't think it's feasible for me to insulate the pipes once they start going up into the wall...

The goal is NOT to reach 170F every time, but rather to not cycle the boiler on/off during calls for heat. The high temp of 170F isn't a goal, it's an artifact of the system radiation size relative to the boiler output, and will only happen during long calls for heat. The 170F just happens to be about where I would expect the heat emittance of your radiation to balance with the heat input by the ES2-3 boiler during a long call for heat say, during recovery from overnight setbacks.

The water should circulate whenever the boiler is over 130F or so. At that output temp it will keep the return water above the 110F minimum needed to protect the ES2 (except during absolute cold starts, but that's to be expected.) During a short call for heat, if starting from 130F or 140F it might never even reach 170F before the thermostat is satisfied, which would be GREAT- it'll be operating at a slightly higher combustion efficiency, and the amount of post-purge to get it down to a lower standby temp would be less.

Insulating all of the heating supply & return plumbing that's accessible to at least R3 does quite a bit for lowering distribution losses. It's even required by code even for single family residential heating system in some states (if rarely enforced).

Posted By Dana1 on 20 Apr 2018 05:12 PM
The goal is NOT to reach 170F every time, but rather to not cycle the boiler on/off during calls for heat.

you lost me here... what does that mean "not cycle the boiler on/off during calls for heat"?? 20 posts later and still clueless...


So I see 2 scenarios here
Scenario 1 - I utilize setbacks either at night, during the day and/or both. Or when it's a true cold start at beginning of season. This would make the boiler run longer WHEN recovering, possibly reaching in our example 170F so I can post purge longer to reduce standby losses. Once the house has recovered from the setback/cold start then it goes into Scenario 2 until the next setback interval
Scenario 2 - I don't use setbacks at all/ there are minimal changes needed to satisfy the call for heat, meaning the boiler will likely run shorter since the disparity won't be as great, but the effective post purge should be shorter because we are starting at a lower temp and thus would lower the residual heat in boiler quicker.
Since the post purge is a timed selection and I don't think I can make it smarter and stop at a certain temp, I'll have to choose whether to be more efficient in Scenario 1, or in Scenario 2 or try and find a middle ground utilizing the post purge interval.
On the bottom of your post

Posted By Dana1 on 20 Apr 2018 05:12 PM
During a short call for heat, if starting from 130F or 140F it might never even reach 170F before the thermostat is satisfied, which would be GREAT- it'll be operating at a slightly higher combustion efficiency, and the amount of post-purge to get it down to a lower standby temp would be less.

That is my Scenario 2. Which is "GREAT." How does that compare to my Scenario 1 which is what you talk about in the top of your post?
Previously I would have thought longer cycles to fill the demand were desirable... Longer burn time, hopefully longer time between calls. But you are saying a short call is ok since we are saying short but not actually short cycling short? So confused.

>you lost me here... what does that mean "not cycle the boiler on/off during calls for heat"?? 20 posts later and still clueless...

If the radiation can emit the full output of the boiler during a call for heat, it burns continuously during the call for heat. If the radiation can't emit the boiler's full output it hits the high limit and turns the burner off, even though there is still an active call for heat. That's why the ES2-3 is a better choice than the ES2-4- the latter puts out more heat than the radiation can emit, and will be forced to cycle. The former puts out less than the radiation's maximum possible output, so it won't cycle.

ES2-3 DOE out: 59,000 BTU/hr

ES2-4 DOE out: 105,000 BTU/hr

radiation output at 180F EWT: 67,000 BTU/hr out.

So with only 59,000 BTU/hr going into the system the water temp can never actually hit the 180F temperature at which the radiation output was estimated, because the boiler can't deliver the full 67,000 BTU/hr. The boiler's temp will stop rising once the radiation is hot enough to emit the full 59,000 BTU/hr, which I'm estimating will be a boiler temp of roughly 170F or a bit less. With 105,000 BTU/hr going into the system it definitely WILL hit the high limit and turn the burner off during a long call for heat, because the radiation can't emit the full 105,000 BTU/hr, so the tempertaure will just keep rising.

When the boiler is started at 130F it's combustion efficiency is about 87%, and falls slowly to about 85% when the temp reaches 170F. The more heat you can get out of the radiation while the system is still cooler by running the circulators allows you to reap a small amount in higher average combustion efficiency. At 130F EWT the radiation only emits about half what it does at 170F, but it's still a substantial amount of heat being delivered before it reaches it's steady state temperature. How long it actually take the ES2-3 to reach that steady state temp depends on the thermal mass in the system, but it'll almost certainly be longer than 5 minutes, maybe longer than 10, and could be more than half the duration of the call for heat.

Any burn time of 10 minutes or longer will pretty much average at the steady-state combustion efficiency. With the radiation you have in place and the thermal mass of the boiler and system water it's never going to be much shorter than that (unless you break it up into multiple zones.) Whether it's a 10-15 minute burn just maintaining the room temp or a 2 hour burn coming back from a deep setback the average combustion efficiency is going to be about the same, within a percent or so. but the cooler start gives you that small advantage, and loses less heat to the basement.

Parking the boiler at a lower temperature at the end of a burn lowers the amount of abandoned heat in the boiler & plumbing that will be lost to the basement between calls for heat, since the difference in boiler temp and basement room temp is lower. That also lowers the basement temp a couple of degrees, which also lowers the heat lost to the outdoors from the basement, and it means the boiler starts at a cooler temp and higher efficiency on the next burn- there's some synergy going on there. Once the basement is insulated the standby and distribution losses will matter a lot less, the basement temperatures will be considerably warmer, but the overall heat loss from the basement will also be dramatically lower. Since the heat is being retained by ~R10 of insulation instead of ~R1 foundation the higher indoors to outdoor temperature difference matter a whole lot less.

With an oversized non-modulating boiler you will still reap real fuel savings from an overnight setback strategy, due to the lower heat loss from the house when it's at a lower temp. When the house is 60F and it's 20F outside it's a 40F difference, when it's 70F indoors it's a 50F difference, and is losing about 25% more heat per hour than the same house at 60F indoors, 20F outdoors. A 5F setback is typically going to net a 4-7% savings in your climate even though it's more like a 10% reduction in actual heat lost (averaged over the outdoor temps of the heating season), depending on just how quickly the indoor temps drop, and the time duration The hit in combustion efficiency from spending more time burning the higher temp is less than 2 percent, and the hit in higher distribution losses maybe another couple percent, but added together those efficiency losses are still add up to a lot less than the savings gained from the lower heat loss of the house at a lower indoor temperature. The better insulated the house, the less difference that makes, but for now it's going to be a real difference.

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